Though it's now been replaced by another one: putting the little terrors down.

An eternal law of nature is that no man, until he becomes a father, can ever possess the first clue about how to hold a baby.

We are all gorillas cradling Stradivariuses, terrified but trying desperately to look like we know what we're doing.

In the past, when I've been in the company of proud new parents in full behold-the-cute-of-our-loins mode, and the dribbly bundle has circulated my way (a polite 'no thanks', as if the hosts were offering round a bowl of cheese-and-onion crisps drizzled in custard, is sadly never an option here), I've adopted one of two strategies.

First, a hand goes under each tiny waggling armpit, and you dangle the petrified blighter aloft so its face is level with yours – then you speak to it directly, maintaining eye-contact at all times, to show its parents you are not afraid. This is fine until you run out of either forearm strength or baby talk; both evaporate alarmingly quickly.

My Plan B – mindful of the midwife's mantra 'always support baby's head' – is the ventriloquist's dummy position, where you perch the poor sprogger upright on your lap and clamp its skull so rigidly it probably thinks it's back in the birth canal.

Oddly, the Child Support Agency offers no advice whatsoever in this regard – so when two of our friends asked my wife and I to babysit their six month old while they slipped off to the cinema last week, it seemed like a golden opportunity to confront my fear of infant-propping in a low-pressure environment. In fact, our evening's dress rehearsal with little Jack would also give us invaluable practice in the associated arenas of feeding, nappy-changing and bedtime. And, as far as I can tell, those three things cover just about all that goes on in the life of a six month old – apart from, I suppose, the odd bit of giggling at car keys.

'Parenting: Take 1' gets off to a good start. Jack's mum has left formula – an unappealingly off-white savoury milkshake – for his dinner, and he gulps it down, eyes glazed over in a nutrient-junkie trance. Big burp. Good boy. Too good, in fact: within minutes the stuff is blasting out the other end like bottle-rocket propulsion, looking and smelling a touch more savoury than before.

My wife changed a nappy a couple of years back, so she heroically takes charge while I hand her various clothy items, announcing their names surgeon's assistant-style. This too goes smoothly (though we actually could have done with a couple of surgeon's masks), and so far, zero tears from Jack. What a champ! And the outlook for me and my wife? Model parents. High five, wife! Now, let's just put the little dude to bed and we can get down to some serious telly before they get back...

Three deafening hours later, our friends arrive home to find me slumped on the sofa cradling their all-cried-out son. I'm gently rocking him back and forth – but it's more Rain Man than doting stand-in dad. Meanwhile, my wife is curled up next to me, a spent maternal force. As we watch the professionals conduct a successful beddy-byesing (lots of cuddles, calming murmuring, no sudden movements) we are humbled and awed, and I realise we're going to need a lot more practice before we get this stuff right – about six months' worth, in fact. Still, I've conquered my fear of holding babies. Though it's now been replaced by another one: putting the little terrors down.